Plastics extrusion is a high volume manufacturing process in which solid plastic material (typically called a resin), in the form of beads or pellets, is continuously fed into a heated tubular chamber or barrel and is moved through the barrel by a drive screw. As the resin is moved through the barrel by the drive screw it is compressed, melted, and forced out of the end of barrel at a steady rate through a die. As the melted resin is pushed through the die, it is formed into a continuous profile having a cross section configuration that matches the die pattern. The melted resin exiting the die is immediately cooled resulting in the re-solidification of the plastic material in the continuous profile.
Plastic extrusion produces products such as pipe/tubing, weather stripping, fence, deck railing, window frames, vinyl siding, plastic wrap, shrink wrap, and many more. Depending on the end product, the extrusion may be a blown into film, wound, spun, folded, rolled, pelletized, plus a number of other possibilities.
The typical plastic extrusion machine includes a heated barrel and a drive screw that extends through an interior bore of the barrel. The screw is driven in rotation in the barrel by a gear transmission, which in turn is powered by a motor. A hopper is attached on top of a proximal end of the barrel and an extruder die is attached over the distal end of the barrel.
In the extrusion process, raw thermoplastic material in the form of small beads or resin is gravity fed into the hopper. Additives such as color additives, film conditioning additives, UV inhibitors can be mixed into the resin prior to the resin arriving at the hopper.
The thermoplastic beads and any additives drop from the hopper, through an opening near the proximal end of the barrel and into the barrel interior bore where they come into contact with the rotating screw. As the screw rotates, it slowly drags the pellets and additives forward through the barrel. The heat from the friction of the screw rotating inside the barrel, together with the external heating of the barrel melts the plastic as it moves forward in the barrel. Further travel of the resin melt through the barrel by the screw rotation thoroughly mixes the melt.
The melt is then extruded into the die. The die gives the final product its profile and is designed so that the plastic melt evenly flows from the cylindrical profile of the interior of the barrel, to the product's profile shape.
The product extruded from the die solidifies quickly. Depending on the end product, the solidification of the product may be achieved by immersion in cooling water, air cooling, or contact with chill roles. Once solid, the product material can then be wound, spun, cut into defined lengths or pelletized depending upon its intended end use.
Most plastic extrusion systems are built to be stationary systems. The present invention is a modular design allowing simple assembly for testing prior to shipment; simple disassembly and placement into standard shipping containers; shipped to site and simple reassembly and placement into production in less than 3 weeks after arrival on site. The present invention is unique in this manner and allows plastics producers to then easily move this system to other locations where plastics production is desired.
Many plastic extrusion processes involve an extruded product having a particular color desired by the end user of the product. Extruding a product of a particular color is accomplished by mixing different colored pellets in certain proportions prior to the pellets being delivered to the hopper of the extrusion machine, or mixing different colors of pellets in certain proportions in addition to pigment additives that are delivered to the hopper to achieve the desired color of the final extruded product.
A downside of producing an extruded product of a particular color is that once the production line of the particular color product is complete, many of the component parts of the extrusion machine must be thoroughly cleaned before beginning another production line of a different color product in order to prevent the color contamination of the subsequent product line. Extrusion machines that typically produce extruded products of different colors are disadvantaged in that, due to the need to thoroughly clean the component parts of the machines between production lines of different extruded products, there is a significant down time of the machines and an associated decrease in the production yield of the machines.
Additionally, because it typically takes between 30 and 60 minutes to thoroughly clean the component parts of an extrusion machine, any short cuts taken to reduce the amount of time in cleaning the machine could result in color contamination of the extruded products from one production line to the next.
What is needed to overcome these disadvantages associated with the typical plastic extrusion machine is a plastic extrusion apparatus that can be quickly changed over from producing an extruded product of one color to an extruded product of another color while reducing or eliminating the possibility of color contamination from the one product to the other product.